Got the infamous MIL driving home on the interstate today. Got the code read, and it's the P0138, only one code, ordered the O2 sensor for that location, should arrive tomorrow. Anyhow, I've been smelling a very faint burnt smell in the cabin, and after sniffing around, I realized it was coming from the cat. It doesn't smell like rotten eggs or anything, just like something is burning and it's very mild. Is the cat frying up?

Another question, I haven't tried getting the cap off yet, but how does she come off? Just pry it or is it threaded? The rubber cap for the O2 sensor wire that is. HOw far/deep do you have to reach to get to the connector?

Thanks all!

 

I don't think a new rear O2 sensor is going to help you. It sounds like you've actually got a basic system problem. This sensor is normally used only as a system monitor. Any performance issues like a miss or black exhaust smoke? If it's a Fed spec car with the sensor behind the main cat, the harness connector is in the floor pan area, accessed by pulling out the floor grommet. This sensor can be a ***** to remove.

 

There is no performance issues, all runs well, everything is smooth, except for the light and that faint smell. No black smoke either, I wouldn't know there was a problem if it wasn't the light.

Yeah, it's a Fed spec car w/ the sensor behind the cat. Where is the floor grommet, under the seat or did you mean the one from the bottom of the car? Thanks!

 

The only grommet is the one under the car, Nissan could've made it a little larger, what were they thinking? Anyhow, it wasn't all that bad, took awhile to fish the connector/harness out, but eventually it did, and it was fairly painless from there.

Oh, and I don't recall smelling the burning smell driving this morning. *knock on wood*

 

check behind your car when you rev and see if its making any noise from the exhaust or anything. have someone rev it up a bit. Also when cats start to go they usually clog up which would make you loose MPG as well as power. A simple way to test this is by taking a piece of cardboard and putting it behind the muffler(not directly on it) as someone revs it. You should feel that the pressure against the cardboard increases as the revs get higher...if not your cat or something else is plugged up a bit.

 

smelly cat... smelly cat... what are they... feeding you? bokbokbok!

I had a smelly cat once. Car threw a code, dealer replaced 02 sensor ONLY... smelly cat no more! 60k miles later, still no smell!